A.O. Smith 310 - NORMAL OPERATION; ACTIVATION; OPERATION; SHUTDOWN

TroubleshootingGuide
5|Page
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3.NORMALOPERATION
Becomingfamiliarwithhowatanklesswaterheaternormally
operates may help to figure out what is wrong with it.
Assuming it is properly installed with appropriate gas, water,
and electric connections, the following is how it should
operate:
1) ACTIVATION
a. Ahotwatertapisopenedenoughthattheflow
sensordetectsaflowratethroughtheheatergreater
thantheactivationpointof0.75gpm.
b. Thefanactivatesafterflowisdetected.
c. Thecomputerchecksforanyproblemswiththeunit
beforestartup.
d. Igniteractivates.You
canhearthebuzzingofthe
sparkigniter.
e. Maingasvalve,proportionalvalve,andsolenoidgas
valveswillopen.Youwillhearadeep“clunkclunk”
noise.
f. Onceaflameisdetected,theredLEDlocatedonthe
computerboardwillactivate.
g. Inamulti‐he ater setup, 
thecontrollerwillactivatethe
nextheaterin2‐4gpmincrements,dependingonthe
settemperature.

2) OPERATION
a. Theproportionalgasvalvewillmodulatebasedontheamountofhotwaterdemandedandthe
temperatureriseneeded.Thefanspeedwillmodulateaswelltocreateanefficientburn.
b. Youwillnoticethatonlypartialsectionsoftheburnerwillbelit.Thisisnormaloperation;there

arethreesectionsontheburnerassembly,andthecomputercontrolstheamountof sections
neededbasedontheflowrateandtemperatureriserequired.

3) SHUTDOWN
a. Theheaterwillshutdownwhenthewaterflowratedropsbelowthedeactivationpointof
0.4gpm.
b. Theheaterwillclosethemaingasvalveandsolenoidgasvalves,extinguishingtheflame.
c. WhentheflamedisappearstheredLEDwillturnoff.
d. Thefanwillincrease
inspeedtopurgetheventingofanyremainingexhaustgases.Thelength
ofpost‐purgecanlastupto1½minutes.
e. Theheatergoesintostandbywaitingfortheprocesstobeginagain.
*Thepurposeofthisdiagramistoillustratethe
tanklesswaterheaterdesignconcepts,and
maynotbeaccuratetoyourmodelsphysical
description.
Figure2